Catheterization of the human heart, as for angioplasty and other cardiac procedures, continues to be used with ever-increasing frequency. Typically, the approach to the right atrium and right ventricle of the heart is accomplished by access through one of the femoral veins, and most commonly the right femoral vein. Presently, access to the left ventricle is typically accomplished by retrograde aortic approach.
The most difficult chamber of the heart to access with a catheter is the left atrium. Access to the left atrium through the pulmonary artery is not possible. Approaches from the left ventricle are difficult, may cause arrhythmias and may present difficulty in obtaining stable catheter positioning. Accordingly, the presently preferred method of accessing the left atrium is through a transseptal approach, that is, catheterization of the right atrium with subsequent penetration of the interatrial septum.
There are some risks attendant to transseptal catheterization, which are risks in addition to those associated with normal heart catheterization. The primary additional risk is that associated with inaccurate identification and localization of the atrial septum. Of course, unknowing, improper placement of the catheter tip prior to the transseptal puncture presents the risk of puncture of tissue other than the interatrial septum. For this reason, catheterization is accompanied by fluoroscopy or other visualizing techniques to assist in properly locating the catheter tip in relation to the septum, in a manner described in detail below.
Generally, the objectives of left atrial access are both diagnostic and therapeutic. One diagnostic use is pressure measurement in the left atrium. In the setting of an obstructed mitral valve (mitral stenosis), left atrial access allows a determination of the pressure difference between the left atrium and left ventricle. Left atrial access also allows entry into the left ventricle through the mitral valve. This is desirable when an artificial aortic valve is in place. The recent advent of aortic valve replacement with mechanical artificial valves, and the increase in the aged population and growing longevity of that population subsequent to aortic valve replacement, brings a greater need to evaluate the late stage functionality of such artificial valves.
Diagnostic measurement of the left ventricular pressures are, therefore, desirable to allow evaluation of mechanical artificial aortic valves post-replacement. It is unsafe to cross these mechanical artificial valves retrograde from the aorta; therefore, access to the left ventricle by the antegrade route using a transseptal puncture is the preferred approach. Once a catheter has been placed in the left atrium using the transseptal approach, access to the left ventricle can be gained by advancing catheters across the mitral valve.
It may be noted that where the mitral or aortic valves have been replaced with a mechanical artificial prothesis, retrograde access to the left atrium is generally viewed to be associated with unacceptably high risk. Of course, there are many diagnostic indications for left atrial pressure measurements in addition to evaluation of functionality of artificial mitral valves. Other diagnostic indications for accessing the left ventricle via the antegrade transseptal approach include aortic stenosis, when a cardiologist is unable to pass a catheter retrograde into the left ventricle, and some disease states where the antegrade approach is considered preferable, such as subaortic obstruction.
Presently, the therapeutic objectives of left atrial access are primarily two-fold. The first is mitral valvuloplasty which represents an alternative to surgical procedures to relieve obstruction of the mitral valve. The second therapeutic objective is for electrophysiological intervention in the left atrium. This procedure, radiofrequency ablation, is relatively new. The usage of this technique is in a growth trend.
Radiofrequency ablation involves the placement of a radiofrequency generating device through a catheter, into various locations of the heart to eradicate inappropriate electrical pathways affecting the heart function. When these locations are in the left atrium, the catheter through which the radiofrequency generator is placed typically is itself placed with transseptal catheterization.
For all of these objectives of left atrial access a sheath is typically introduced into the left atrium through which appropriate catheters are placed. Especially for radiofrequency ablation of the left atrium, considerable manipulation of the tip of the catheter across the atrial septum is typically required. The risk associated with the manipulation of the catheter tip in the left atrium is inadvertent retraction of the sheath through the septum and back into the right atrium. Typically, because of the risk to the patient engendered by transseptal puncture and because of the common use of an anticoagulant to reduce the possibility of embolism after catheter access into the left atrium, it is desirable that only one transseptal puncture be attempted during the procedure. Only infrequently will the surgeon attempt a second transseptal approach during a single procedure.
Moreover, where retraction of the sheath tip back through the atrial septum is undetected, further manipulation under the mistaken belief of positioning in the left atrium presents other risks to nearby tissue. Especially for radiofrequency ablation of areas of the left atrium relatively near the atrial septum, the risk of inadvertent retraction of the sheath into the right atrium is heightened.
Following previously known procedures, the problem of inadvertent withdrawal of the catheter tip from the left atrium, through the atrial septum, and back into the right atrium remains a risk.
It is an objective of the present invention to provide a retaining means for retaining the distal tip of a sheath which has been placed through a septum, such as the interatrial septum, across the septum, in the left atrium during left heart procedures.
It is another objective of the present invention to provide retaining means for transseptal catheterization which is selectively deployable and retractable.
It is yet a further objective of the present invention to provide a method of transseptal catheterization, with subsequent manipulation of instruments in the left atrium, which assures proper positioning of the distal tip of the sheath through which those instruments are passed, within the left atrium, while avoiding inadvertent withdrawal of the sheath tip back through the septum.